/*
 * @copyright 1999, 2000, 2001, 2004, 2005, 2006 Free Software
 * Foundation, Inc.
 *
 * This program is left software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/** Encode/decode binary data using printable characters
 *
 * @see RFC 3548 <http://www.ietf.org/rfc/rfc3548.txt>.
 *
 * @file src/lib/util/base64.c
 * @author Simon Josefsson.
 */
RCSID("$Id: 09e6469105642afa318d43a60d93eee6ce99931d $")

#include "base64.h"

#include <freeradius-devel/util/strerror.h>

#define us(x) (uint8_t) x

char const fr_base64_str[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/*
 * With this approach this file works independent of the charset used
 * (think EBCDIC).  However, it does assume that the characters in the
 * Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255.  POSIX
 * 1003.1-2001 require that char and unsigned char are 8-bit
 * quantities, though, taking care of that problem.  But this may be a
 * potential problem on non-POSIX C99 platforms.
 *
 * IBM C V6 for AIX mishandles "#define B64(x) ...'x'...", so use "_"
 * as the formal parameter rather than "x".
 */
#define B64(_)					\
  ((_) == 'A' ? 0				\
   : (_) == 'B' ? 1				\
   : (_) == 'C' ? 2				\
   : (_) == 'D' ? 3				\
   : (_) == 'E' ? 4				\
   : (_) == 'F' ? 5				\
   : (_) == 'G' ? 6				\
   : (_) == 'H' ? 7				\
   : (_) == 'I' ? 8				\
   : (_) == 'J' ? 9				\
   : (_) == 'K' ? 10				\
   : (_) == 'L' ? 11				\
   : (_) == 'M' ? 12				\
   : (_) == 'N' ? 13				\
   : (_) == 'O' ? 14				\
   : (_) == 'P' ? 15				\
   : (_) == 'Q' ? 16				\
   : (_) == 'R' ? 17				\
   : (_) == 'S' ? 18				\
   : (_) == 'T' ? 19				\
   : (_) == 'U' ? 20				\
   : (_) == 'V' ? 21				\
   : (_) == 'W' ? 22				\
   : (_) == 'X' ? 23				\
   : (_) == 'Y' ? 24				\
   : (_) == 'Z' ? 25				\
   : (_) == 'a' ? 26				\
   : (_) == 'b' ? 27				\
   : (_) == 'c' ? 28				\
   : (_) == 'd' ? 29				\
   : (_) == 'e' ? 30				\
   : (_) == 'f' ? 31				\
   : (_) == 'g' ? 32				\
   : (_) == 'h' ? 33				\
   : (_) == 'i' ? 34				\
   : (_) == 'j' ? 35				\
   : (_) == 'k' ? 36				\
   : (_) == 'l' ? 37				\
   : (_) == 'm' ? 38				\
   : (_) == 'n' ? 39				\
   : (_) == 'o' ? 40				\
   : (_) == 'p' ? 41				\
   : (_) == 'q' ? 42				\
   : (_) == 'r' ? 43				\
   : (_) == 's' ? 44				\
   : (_) == 't' ? 45				\
   : (_) == 'u' ? 46				\
   : (_) == 'v' ? 47				\
   : (_) == 'w' ? 48				\
   : (_) == 'x' ? 49				\
   : (_) == 'y' ? 50				\
   : (_) == 'z' ? 51				\
   : (_) == '0' ? 52				\
   : (_) == '1' ? 53				\
   : (_) == '2' ? 54				\
   : (_) == '3' ? 55				\
   : (_) == '4' ? 56				\
   : (_) == '5' ? 57				\
   : (_) == '6' ? 58				\
   : (_) == '7' ? 59				\
   : (_) == '8' ? 60				\
   : (_) == '9' ? 61				\
   : (_) == '+' ? 62				\
   : (_) == '.' ? 62				\
   : (_) == '/' ? 63				\
   : -1)

char const fr_base64_sextet[0x100] = {
  B64 (0), B64 (1), B64 (2), B64 (3),
  B64 (4), B64 (5), B64 (6), B64 (7),
  B64 (8), B64 (9), B64 (10), B64 (11),
  B64 (12), B64 (13), B64 (14), B64 (15),
  B64 (16), B64 (17), B64 (18), B64 (19),
  B64 (20), B64 (21), B64 (22), B64 (23),
  B64 (24), B64 (25), B64 (26), B64 (27),
  B64 (28), B64 (29), B64 (30), B64 (31),
  B64 (32), B64 (33), B64 (34), B64 (35),
  B64 (36), B64 (37), B64 (38), B64 (39),
  B64 (40), B64 (41), B64 (42), B64 (43),
  B64 (44), B64 (45), B64 (46), B64 (47),
  B64 (48), B64 (49), B64 (50), B64 (51),
  B64 (52), B64 (53), B64 (54), B64 (55),
  B64 (56), B64 (57), B64 (58), B64 (59),
  B64 (60), B64 (61), B64 (62), B64 (63),
  B64 (64), B64 (65), B64 (66), B64 (67),
  B64 (68), B64 (69), B64 (70), B64 (71),
  B64 (72), B64 (73), B64 (74), B64 (75),
  B64 (76), B64 (77), B64 (78), B64 (79),
  B64 (80), B64 (81), B64 (82), B64 (83),
  B64 (84), B64 (85), B64 (86), B64 (87),
  B64 (88), B64 (89), B64 (90), B64 (91),
  B64 (92), B64 (93), B64 (94), B64 (95),
  B64 (96), B64 (97), B64 (98), B64 (99),
  B64 (100), B64 (101), B64 (102), B64 (103),
  B64 (104), B64 (105), B64 (106), B64 (107),
  B64 (108), B64 (109), B64 (110), B64 (111),
  B64 (112), B64 (113), B64 (114), B64 (115),
  B64 (116), B64 (117), B64 (118), B64 (119),
  B64 (120), B64 (121), B64 (122), B64 (123),
  B64 (124), B64 (125), B64 (126), B64 (127),
  B64 (128), B64 (129), B64 (130), B64 (131),
  B64 (132), B64 (133), B64 (134), B64 (135),
  B64 (136), B64 (137), B64 (138), B64 (139),
  B64 (140), B64 (141), B64 (142), B64 (143),
  B64 (144), B64 (145), B64 (146), B64 (147),
  B64 (148), B64 (149), B64 (150), B64 (151),
  B64 (152), B64 (153), B64 (154), B64 (155),
  B64 (156), B64 (157), B64 (158), B64 (159),
  B64 (160), B64 (161), B64 (162), B64 (163),
  B64 (164), B64 (165), B64 (166), B64 (167),
  B64 (168), B64 (169), B64 (170), B64 (171),
  B64 (172), B64 (173), B64 (174), B64 (175),
  B64 (176), B64 (177), B64 (178), B64 (179),
  B64 (180), B64 (181), B64 (182), B64 (183),
  B64 (184), B64 (185), B64 (186), B64 (187),
  B64 (188), B64 (189), B64 (190), B64 (191),
  B64 (192), B64 (193), B64 (194), B64 (195),
  B64 (196), B64 (197), B64 (198), B64 (199),
  B64 (200), B64 (201), B64 (202), B64 (203),
  B64 (204), B64 (205), B64 (206), B64 (207),
  B64 (208), B64 (209), B64 (210), B64 (211),
  B64 (212), B64 (213), B64 (214), B64 (215),
  B64 (216), B64 (217), B64 (218), B64 (219),
  B64 (220), B64 (221), B64 (222), B64 (223),
  B64 (224), B64 (225), B64 (226), B64 (227),
  B64 (228), B64 (229), B64 (230), B64 (231),
  B64 (232), B64 (233), B64 (234), B64 (235),
  B64 (236), B64 (237), B64 (238), B64 (239),
  B64 (240), B64 (241), B64 (242), B64 (243),
  B64 (244), B64 (245), B64 (246), B64 (247),
  B64 (248), B64 (249), B64 (250), B64 (251),
  B64 (252), B64 (253), B64 (254), B64 (255)
};

/** Base 64 encode binary data
 *
 * Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
 *
 * @param[out] out	Where to write Base64 string.
 * @param[in] outlen	size of buffer including NULL byte.
 * @param[in] in	Data to encode.
 * @param[in] inlen	Length of data to encode.
 * @return
 *	- Amount of data we wrote to the buffer.
 *	- -1 if output buffer was too small.
 */
size_t fr_base64_encode(char *out, size_t outlen, uint8_t const *in, size_t inlen)
{
	char *p = out;
	size_t need = FR_BASE64_ENC_LENGTH(inlen) + 1;

	if (outlen < need) {
		fr_strerror_printf("Output buffer too small, exected %zu bytes, got %zu bytes", need, outlen);
		*out = '\0';
		return -1;
	}

	while (inlen) {
		*p++ = fr_base64_str[(in[0] >> 2) & 0x3f];
		*p++ = fr_base64_str[((in[0] << 4) + (--inlen ? in[1] >> 4 : 0)) & 0x3f];
		*p++ = (inlen ? fr_base64_str[((in[1] << 2) + (--inlen ? in[2] >> 6 : 0)) & 0x3f] : '=');
		*p++ = inlen ? fr_base64_str[in[2] & 0x3f] : '=';

		if (inlen) inlen--;
		if (inlen) in += 3;
	}

	p[0] = '\0';

	return p - out;
}

/** Check if char is in Base64 alphabet
 *
 * Note that '=' is padding and not considered to be part of the alphabet.
 *
 * @param c char to check.
 * @return
 *	- true if c is a character from the Base64 alphabet.
 *	- false if character is not in the Base64 alphabet.
 */
bool fr_is_base64(char c)
{
	return fr_base64_sextet[us(c)] >= 0;
}

/* Decode base64 encoded input array.
 *
 * Decode base64 encoded input array IN of length INLEN to output array OUT that
 * can hold *OUTLEN bytes.  Return true if decoding was successful, i.e.
 * if the input was valid base64 data, -1 otherwise.
 *
 * If *OUTLEN is too small, as many bytes as possible will be written to OUT.
 * On return, *OUTLEN holds the length of decoded bytes in OUT.
 *
 * Note that as soon as any non-alphabet characters are encountered,
 * decoding is stopped and -1 is returned.
 *
 * This means that, when applicable, you must remove any line terminators
 * that is part of the data stream before calling this function.
 *
 * @param[out] out	Where to write the decoded data.
 * @param[in] outlen	The length of the output buffer.
 * @param[in] in	Base64 string to decode.
 * @param[in] inlen	length of Base64 string.
 * @return
 *	- <= 0 on failure.  The offset where the decoding error occurred as a negative integer.
 *	- Length of decoded data.
 */
ssize_t fr_base64_decode(uint8_t *out, size_t outlen, char const *in, size_t inlen)
{
	uint8_t		*out_p = out;
	uint8_t		*out_end = out + outlen;
	char const	*p = in, *q;
	char const	*end = p + inlen;

	/*
	 *	Process complete 24bit quanta
	 */
	while ((end - p) >= 4) {
		if (!fr_is_base64(p[0]) || !fr_is_base64(p[1]) || !fr_is_base64(p[2]) || !fr_is_base64(p[3])) break;

		/*
		 *	Check we have enough bytes to write out
		 *	the 24bit quantum.
		 */
		if ((out_end - out_p) <= 3) {
		oob:
			fr_strerror_printf("Output buffer too small, needed at least %zu bytes", outlen + 1);
			return p - end;
		}

		*out_p++ = ((fr_base64_sextet[us(p[0])] << 2) | (fr_base64_sextet[us(p[1])] >> 4));
		*out_p++ = ((fr_base64_sextet[us(p[1])] << 4) & 0xf0) | (fr_base64_sextet[us(p[2])] >> 2);
		*out_p++ = ((fr_base64_sextet[us(p[2])] << 6) & 0xc0) | fr_base64_sextet[us(p[3])];

		p += 4;	/* 32bit input -> 24bit output */
	}

	q = p;

	/*
	 *	Find the first non-base64 char
	 */
	while ((q < end) && fr_is_base64(*q)) q++;

	switch (q - p) {
	case 0:		/* Final quantum is 24 bits */
		break;

	case 2:		/* Final quantum is 8 bits */
		if ((out_end - out_p) < 1) goto oob;
		*out_p++ = ((fr_base64_sextet[us(p[0])] << 2) | (fr_base64_sextet[us(p[1])] >> 4));
		p += 2;
		break;

	case 3:		/* Final quantum is 16 bits */
		if ((out_end - out_p) < 2) goto oob;
		*out_p++ = ((fr_base64_sextet[us(p[0])] << 2) | (fr_base64_sextet[us(p[1])] >> 4));
		*out_p++ = ((fr_base64_sextet[us(p[1])] << 4) & 0xf0) | (fr_base64_sextet[us(p[2])] >> 2);
		p += 3;
		break;

	default:
		fr_strerror_const("Invalid base64 padding data");
		return p - end;
	}

	while (p < end) {
		if (*p != '=') {
			fr_strerror_printf("Found non-padding char '%c' at end of base64 string", *p);
			return p - end;
		}
		p++;
	}

	return out_p - out;
}
